AK260

Thanks Steve, that’s super interesting and I will check all those items. The diaphragm on mine went from not moving at all, to moving as if it was grinding with sand crunching inside. I Hence why I decided to soak / de-rust. Since the liquid didn’t get in there, I suspect that my brute force and ignorance in moving it by hand may have freed it off a bit. Once the rust is cleaned off, I’ll be able to better see the things you mentioned above and report back. BTW that paper gasket on mine will be toast by the time I finish with it all. What did you use? I have gasket material sheets from which I can just make a new one and seal it with Hylomar Blue or a liquid gasket of sorts. But I also suspect such things can change the tone too, right?

Ha! Yes good point. The diaphragm and gasket were totally sealing the inside. In fact it only came apart when I tried to undo the centre nut with a socket set and the outside ring / bolts removed - it was PROPERLY stuck/ sealed together. Plus the bits sandwiched together seem to have been impervious until taken apart. Probably a side effect of 40+ years of English weather! So it seems there was an air bubble inside - otherwise the zinc plating would have gone also. You’ll notice on the before photo of the rear that there was a bit without rust on the back. This was yellow zinc which after just a couple of hours became a metallic colour you see in the photo.

I’ve been meaning to fix my silent horn since I bought the car but it’s just been sitting in the corner of the garage bugging me. So I dropped it into some lemon juice and salt mix before we went camping for a week. I love this method of de-rusting: cheap and gentle but it gets into all the places I can’t with a brush! This is the before photos (well after a couple of hours of soaking when I realised I hadn’t done a “before”) Then when we got back, I fished this out (pic is after a rub down with micro fibre cloth to remove residues etc) - I love the fact that even the paint has been stripped off and you can read the original stamping on the back: Now the fully rusted in screws just turned without any real resistance! One did have to get drilled out though as it was rounded off too much from previous efforts. I connected it up and for the first time in my ownership it made a sound - albeit a tad muffled. Pushing it in and out by hand I could hear rust, so I took the whole thing apart to discover - wait for it - more rust!! So back they all went into the lemon and salt mix let’s see what they look like tomorrow morning!

Ron - you’re a super good man! I love the fact that you are helping someone doing it for themselves even though you make money from repairing these. Few of you in the world fella, well done!

To your point - this thing was literally paper thin in areas - probably why the do not touch sign was on it - and I was shocked how much it sold for 6 year ago!! But never underestimate the power of of having will and skill! If the OP can do metalwork to a high standard then a tonne of cost is saved.

This is my new FAVOURITE all-time thread. Thanks Kats and Alan for sharing such brilliant info. What I don’t understand is - and bear with me pls, I know little about aerodynamics - given that the engine bay pressurises does the blunt nose improve cooling also? And does the standard under tray improve the pressurisation situation? (Apologies if it’s covered in the magazine articles that I haven’t had a chance to read yet). A very experienced member of the UK club (the late Mr. F) used to tell me that the under tray also affect the cooling efficiency, so I’m wondering if this was the reason?

Well it was most definitely 17mm. So I got the smallest pulley I could realistically get onto our alternators (47mm OD 40mm PCD) and bored it out to make it fit. I took a little too much material out of my first attempt - broke as soon as I tried to flex it! ;) It’s sorted out my discharging at idle issues and the voltage is a lot more stable. With the ATi damper and pulley (70mm) I now get a 1:1.5 ratio meaning my alternator is actually generating at an idle of 1k rpm. Now to find a new belt as it’s right on the limit of the adjuster.

So gang mine arrived today via Amazon - happy to report the Innovate one seems to be genuine!

We are still lucky enough to have ethanol free super unleaded at Esso in the Southeast of England. That’s the ONLY fuel I use. But our other super unleaded is 5% ethanol. Just been out for a blast to test some tuning I did today and when parked up I popped the bonnet to check the fuel rail. Front of engine mounting hanger (welded) without insulators, was cool to the touch. Mid part of the rail boiling hot! I appreciate the timing chain part of the head will be cooler but the fuel rail at that point was way cooler than that section of the head. So I suspect the majority of the issue is radiated heat. Isolating the rail hangers with fibre washers in the past - I found didn’t make much of a difference and over time they broke up and caused false air / vac leaks on the intake manifold. So better washers for insulation need to be thought about! Maybe mica washers!? Sent from my iPhone using Tapatalk Pro

Mine has them too but there are two “hangers” that definitely came out of the factory without them. :( Obviously my car has been tinkered with by POs, hence it came with round top 3 screws rather than the flat tops (and the most deliciously ported head). So I can’t be sure what year fuel rail I have. Either way, I’m sure as stock they had some issues in hot climates but with the modifications and performance we’re extracting these days, we are just exacerbating any minor / inherent heat issues.

Not at all likely!!! As you can see on mine, it bolts up metal on metal to one of the hottest part of the head (cyl5/6) and directly transfers heat into that block thing, nicely heating up the fuel on its way to the rear carb ! :( And don’t even get me started on the middle one that unlike the others doesn’t have an insulator of any sort. So not only do you have heat radiated from the manifold below, you also have metal on metal conduction from the head. I don’t wish to upset anyone but I do feel this is a flawed design - probably a common design of the era? I’ve literally spent the afternoon thinking about this and redesigning mine to go round the other side, behind the engine, then come to the carbs behind the heat-shield and be properly isolated from metal on metal contact. I’m sure it won’t solve heat-soak issues but should alleviate many other heat related problems. You could of course re-route from behind the engine if you don’t use the mech pump, but I like having a mech pump in the circuit. And my mech fan and my mech water pump. Analogue man in a digital world and all that. Will definitely share when / if I ever get the time to build an alternative fuel rail. Ordered the parts so no excuses now ;)

Gosh - that really sounds like engine bay hell!!!!! I can only Imagine what all that heat must have done to other rubber hoses / components! Speaking of glowing manifolds - one dark evening I had the car warming up on the choke at around 2k rpm and came back 3-5 mins later to find this …. Which is what makes me think whatever fuel line is used above the primaries is going to suffer with that radiated heat - especially when on full chat for prolonged periods as you experienced. The AFR in the photo was around 12.5 - I checked as my instant thought was “it must be super lean to cause that much visible heat”. I often wonder why the engineers didn’t run the rails on the “cool side” of the engine.

Thanks for that detailed reply Jeff - much appreciated. My vapour lock issues were mainly due to idling on hot days or stopping for fuel. I found 90% of all issues was fixed by a home made heat shield that protects the carbs and float bowls. In fact my carbs are fridge cool to touch after a run and often have condensation on the domes. BUT - the super heated fuel rails bother me both from a performance and vapour lock perspective. If going the rubber route, I would suggest running it round the back of the engine and closer to the carbs where the heat-shield protects the rubber from the most extreme temps. Here’s a pic of my homemade heat-shield (those trumpets were experimental at the time and totally rubbish)! I guess the key thing is to find a way to ensure the rubber line isn’t vibrating / fouling against things that vibrate.

I was told by an old racer that they used tap fibre washers to good effect. Having said that, you have to be careful they don’t deteriorate over time and cause vacuum leaks. I tried this and it made little difference. The real problem as you said is the radiated heat from the air chairs manifold directly below it. Mine sits at a reasonable temp when driving or with the engine running - but turn the engine off for 5 mins to fill up and the rails become BURNING hot to the touch!! I imagine the fuel is beyond vaporised in there!! Great to hear the rubber solution worked well - any pictures? Did you route round the back of the engine or the same routing as stock config?

Thanks buddy, that’s great.

Hello gang! Been about 2 years since I properly saw the Z and played with it. But being on gardening leave, I’ve finally got time again. I’m using an ATi super racing damper, which has a 70mm pulley - to reduce parasitic losses. Yay for free BHP and boo for alternator spinning at just less than half speed, not producing charge at idle revs! Most alternators do nothing of note below 1200-1400 shaft RPMs. To combat this, I had it professionally rewound to produce earlier + modified a 63mm pulley on a lathe. This reduced the issue but the voltage needle still dances at idle until about 1300rpm which I don’t like, especially as the lights dim then go bright with rising revs. So, I’m about to fashion 2 other pulleys to experiment with - one with a 50mm OD and one with 40mm. To do this I need to drill out the centre of a blank pulley - for the life of me I can’t recall the size. 17mm seems to ring a bell and a nut I “think” I bought for the alternator but never used seems to confirm it. Or is it 18mm to account for the thread depth? But I thought I would ask here as someone may know and save me taking the alternator off the car and removing the pulley to measure. So come on! Fess up! Who else is man enough to publicly claim they have a 17mm shaft!?

Really well put! Being in Financial Services, I see this all the time. Especially when the Private Equity and Venture Capitalists get stuck in. It’s all about ROE and ROCE rather than maintaining brand values / quality is an after thought. The R is return which by definition means profit and if you’re not raising prices or organic market share the you get it through cost cutting. All acquisitions must be seen to add synergistic value and better returns and the fastest way to make a CEO look good for their acquisition is to cut cost. “Cost of quality” AKA returns rarely makes it to shareholder reporting ;) Now then back on topic. I’m now worried !! Will report back when I get mine.

Also on eBay at the same price I paid many years ago! https://www.ebay.co.uk/itm/131982341550?

Now that’s really moved on from when I last considered it about 10 years ago!! Looks the business and probably sounds great. I would be tempted to get that and keep your appreciating asset of a stock item ! Being a geek I manually replaced the electronics inside mine and added a dish sized flat sub under the passenger seat to overcome the effects of the exhaust - as I kept the stock sized (modern) speakers and the minimal bass was totally lost with the engine running. In Phase Car Audio USW10 300W 10" Underseat Ultra Slim Compact Active Subwoofer System, Die-Cast Aluminium , Black https://amzn.eu/d/41hVB3V Oh and to avoid drilling the floor I used industrial strength Velcro :p But truthfully I barely ever use the radio. The engine note is just too glorious. But equally, I don’t really drive it for very long on motorways, where I imagine it comes into its own.

I’m with granny - unless you want the stock look, I don’t think it’s function is really worth it. Before I went with a different air box and full cold air intake, I had a plastic intake pipe going from the exhaust part of the box to the rad panel, bringing in cold air from the front of the car - I figured every little helps.

This is also a good resource for comparison of needles http://www.mintylamb.co.uk/suneedle/

A good discussion here https://www.classiczcars.com/forums/topic/43876-n49-n54-needles/ The N27/54 needles don’t appear on SU needle charts as I believe (and happy to be corrected) they were not SU needles, they were Hitachi / Datsun needles. As mentioned above, the best bet is to mark and measure them at 3mm intervals (stations). I did this with my modified SM needles to model them on excel and compare to other off the shelf (SU) needles. It only takes 10 mins to do and then you can post it here for anyone else looking in the future too! :p I then went a bit nuts and tried to video what positions where in use at what loads / RPMs ;)

Given the PO of my car had installed rubber pipes from fuel tank to filter and ran them over the rear ARB (!!!) I decided to make my own using a pipe bender and 4m of aluminium fuel pipe. It took some time to make a single piece from tank to filter but worth it if you have the patience and time. On a late 260z fuel and brake lines run by the frame rails so more easily accessible but I would say don’t fear jacking the car up and getting under it (with axle stands of course). You may be able to remove a couple of the clamps and drop the line enough to see if you can get a 1/4 turn on those nuts which may well fix the problem.

Can’t comment on the banjo question but the needles on all 3 sets of my carbs just slide out when undone. I strongly suspect you are battling corrosion. Just use the usual penetrating oils etc and soak then gently try to move them out. Good luck fella.

That I don’t doubt for a second - I just don’t trust eBay and other sellers to be doing that level of attention to detail / design. So my point really is more about being clear about the standard to which these things are made.